Multi-band energy harvesting system

ABSTRACT

A multi-band energy harvesting system is provided. The system includes a plurality of harvesting antennas, wherein each of the plurality of harvesting antennas, operates a specific frequency band; and a plurality of harvesting units, wherein each of the plurality of harvesting units is coupled to a respective harvesting antenna and adapted to harvest energy at the specific frequency band of the respective harvesting antenna.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/792,581 filed on Jan. 15, 2019, the contents of which are herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to energy harvesting and morespecifically to Internet of Things (IoT) sensors.

BACKGROUND

The Internet of things (IoT) is the inter-networking of physicaldevices, vehicles, buildings, and other items embedded with electronics,software, sensors, actuators, and network connectivity that enable theseobjects to collect and exchange data. IoT is expected to offer advancedconnectivity of devices, systems, and services that goes beyondmachine-to-machine (M2M) communications and covers a variety ofprotocols, domains, and applications.

IoT can be encapsulated in a wide variety of devices, such as heartmonitoring implants; biochip transponders on farm animals; automobileswith built-in sensors; automation of lighting, heating, ventilation, airconditioning (HVAC) systems; and appliances such as washer/dryers,robotic vacuums, air purifiers, ovens or refrigerators/freezers that useWi-Fi for remote monitoring. Typically, IoT devices encapsulate wirelesssensors or a network of such sensors.

Most IoT devices are wireless devices that collect data and transmitsuch data to a central controller. There are a few requirements thatmust be met to allow widespread deployment of IoT devices. Suchrequirements include reliable communication links, low energyconsumption, and low maintenance costs.

An alternative to using batteries, is a power supply which may beharvested from sources such as light, movement, and electromagneticpower such as existing radio frequency transmissions. The harvestedpower is stored in a capacitor or a rechargeable battery, and typicallymanaged by a power management unit (PMU). A PMU is a circuit thatperforms general circuit power related operations, such as supplyregulation, voltage and current references, power on indication,brown-out indication, power modes control, management of power storageunits, and more.

Specifically, in power harvesting systems, a PMU provides energy storageand voltage threshold crossing indications based on measurement of thevoltage over the storage capacitors.

FIG. 1 shows a diagram of a conventional harvester system 100 based on aharvester 110. The harvester 110 is coupled to a PMU 120 including aSchmitt trigger 122. The harvester 110 receives RF signals transmittedby external resources. The energy of the received RF signals charges acapacitor 112, where the conversion of energy to current is performed bymeans of a voltage multiplier 114. A voltage multiplier is an electricalcircuit that converts AC electrical power to a DC voltage and cascadesits DC outputs to multiply the output voltage level, typically using anetwork of capacitors and diodes or switches. An example for such amultiplier is a Dickson multiplier.

The PMU 120 determines when the voltage level at the capacitor 112 issufficient enough so that the harvester system 100 can run computingtasks, and transmit, and/or receive signals. For example, a referencevoltage threshold (Vref) is compared to the voltage level (Vin) at thecapacitor 112. Once the voltage level Vin is over the threshold (Vref),the Schmitt trigger 122 switches from zero to one, signaling that theharvester 110 device has sufficient power.

A Schmitt trigger 122 is a comparator circuit with a hysteresis 124implemented by applying positive feedback to the noninverting input of acomparator or differential amplifier. Here, a Schmitt trigger is anactive circuit which converts an analog input signal to a digital outputsignal via a comparator and has a hysteresis. As such, power is requiredto operate the Schmitt trigger 122. The power is provided by theharvester 110.

Omitting the batteries from IoT devices is of interest because of theircost, size, lack of durability to environmental effects (e.g. water,humidity), and their short lifetime which requires accessibility forreplacement. The problem with the harvester's design disclosed in therelated art is that, such a harvester only provides a single resource ofenergy. When no signals are received at the frequency that an antenna ofa single harvester is tuned to, often the case no energy is able to beharvested at all. In order to optimize performance, a harvester andantenna should operate at a high-quality factor resonance. Thus, a wideband antenna, may not be applicable.

It would therefore be advantageous to provide a solution that wouldharvest energy from multiple sources in IoT devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter disclosed herein is particularly pointed out anddistinctly claimed in the claims at the conclusion of the specification.The foregoing and other objects, features, and advantages of thedisclosed embodiments will be apparent from the following detaileddescription taken in conjunction with the accompanying drawings.

FIG. 1 is a diagram of a conventional harvester system.

FIG. 2 is a block diagram of a multiband energy harvester according tosome embodiments.

FIG. 3 is a block diagram of a wireless IoT chip with multiband energyharvester according to some embodiments.

FIG. 4 is a diagram of a multi-band energy harvester designed accordingto one embodiment.

FIG. 5 is a diagram of a multi-band energy harvester designed accordingto another embodiment.

SUMMARY

A summary of several example embodiments of the disclosure follows. Thissummary is provided for the convenience of the reader to provide a basicunderstanding of such embodiments and does not wholly define the breadthof the disclosure. This summary is not an extensive overview of allcontemplated embodiments, and is intended to neither identify key orcritical elements of all embodiments nor to delineate the scope of anyor all aspects. Its sole purpose is to present some concepts of one ormore embodiments in a simplified form as a prelude to the more detaileddescription that is presented later. For convenience, the term “someembodiments” or “certain embodiments” may be used herein to refer to asingle embodiment or multiple embodiments of the disclosure.

Certain embodiments disclosed herein include a multi-band energyharvesting system. The system comprises a plurality of harvestingantennas, wherein each of the plurality of harvesting antennas operatesat a specific frequency band; and a plurality of harvesting units,wherein each of the plurality of harvesting units is coupled to arespective harvesting antenna and adapted to harvest energy at thespecific frequency band of the respective harvesting antenna.

Certain embodiments disclosed herein include a battery-free wirelessdevice, comprising: a multi-band energy harvesting system adapted toharvest energy from over-the-air signals transmitted in differentfrequency bands; and a sensor powered by the harvested energy.

DETAILED DESCRIPTION

It is important to note that the embodiments disclosed herein are onlyexamples of the many advantageous uses of the innovative teachingsherein. In general, statements made in the specification of the presentapplication do not necessarily limit any of the various claimedembodiments. Moreover, some statements may apply to some inventivefeatures but not to others. In general, unless otherwise indicated,singular elements may be in plural and vice versa with no loss ofgenerality. In the drawings, like numerals refer to like parts throughseveral views.

Some embodiments use standard radio transmission in the same system. Inan example embodiment, a Bluetooth Low Energy may transmit simultaneousto energy harvesting. In another example, some embodiments may operateas part of a duty cycled system, so that transmission and otheroperations do not rely on simultaneous harvesting. For example, part ofthe time the antennas may be tuned to receive/transmit and the otherpart of the time the antenna may be tuned to harvest energy.

FIG. 2 illustrates an example block diagram of a multiband energyharvester 200 disclosed according to some embodiments. The harvester 200includes a plurality of band-specific harvesting units 210-1 through210-N (where N is an integer greater than 1). Each harvesting unit 210-1through 210-N is respectively coupled to antenna 220-1 through 220-N.The band-specific harvesting units 210-1 through 210-N are referred toindividually as a harvesting unit 210 or collectively as harvestingunits 210 for simplicity. Further, the antennas 220-1 through 220-N maybe referred to individually as an antenna 220 or collectively asantennas 220 for simplicity. Energy harvested by the harvesting units210 may be stored as an energy storage unit, such as the capacitor 230.

Electromagnetic energy is available from existing wireless signals thatexist in the environment of the harvester 200. Such wireless signals maycomply with known wireless standards, such as Wi-Fi (IEEE 802.11) whichoperates at the 2.4 GHz and 5-6 GHz bands, the BLE protocol whichoperates in the 2.400-2.4835 GHz band, Wi-Gig which operates at the 60GHz band, cellular signals that comply with cellular standards (such as2G, 3G, LTE, 4G, 5G, 5G mmWave, and the like), and Industrial,Scientific, and Medical (ISM) frequency band.

As each wireless standard operates at a different frequency anddifferent frequency channels within its allocated band(s), each antenna220 is designed to receive signals at a specific frequency band. Forexample, the antenna 220-1 may be designed to receive signals at the BLEband (2.400-2.4835 GHz) and the antenna 220-N may be designed to receivesignals at the Wi-Fi 2.4 GHz band. Similarly, the antenna 220-1 may bedesigned to receive signals at the cellular 1.7-2GHz bands.

In some embodiments, a number of antennas 220 may be designed to receivesignals at the same frequency band. For example, antennas 220-1 and220-N may operate at 2.4 GHz.

It should be noted that although the antenna 220 is designed to aspecific frequency band, the respective harvesting unit 210 should betuned to a center frequency at which the signal is received. In order tooptimize performance, a harvesting unit 210 and a respective antenna 220should operate at resonance. To this end, in some embodiments, a tuningmechanism (not shown) is included in the harvester 200.

The tuning mechanism may be utilized to tune each or some of theharvesting units 210 to operate at resonance with the frequency of thereceived harvesting signals. In an embodiment, the tuning mechanism isdesigned to be activated at very low energy levels, so that the tuningmay be initiated immediately.

The harvester 200 may be integrated in an IoT sensor or a wireless IoTchip (not shown). Specifically, the antennas are fabricated or printedon the same substrate (inlay) that carries the wireless IoT chip. Thewireless IoT chip typically receives and transmits wireless signalsusing, for example, the BLE communication standard. In thisconfiguration, one of the antennas 220 may be served as thetransmit/receive antenna of the wireless IoT chip. To this end, a dutycycle between harvesting and receiving/transmitting is implemented. Thatis, transmission and receiving may occur in non-harvesting time periods.

In some embodiments, different signals may be received and/ortransmitted according to an assigned duty cycle. For example, the BLEmay be turned on and off at various points, or cellular communications.In one example, Wi-Fi may be used for energy harvesting, otherwise BLEmay be used or activated. Duty cycle assignments may be based onproximity to a source of BLE transmission. Duty cycle percentage targetsmay be assigned in any number of ways as described herein.

In certain configurations, a dedicated antenna is utilized as thetransmit/receive antenna. Thus, each of the antennas 220 serve forenergy harvesting. An example for such a wireless IoT chip implementedwith the harvester 200 and a dedicated transmit/receive antenna isprovided in FIG. 3.

In some embodiments, each harvesting unit 210 includes a voltagemultiplier (not shown) that may be directly coupled to the respectiveantenna 220 and the energy storage 230. The voltage multiplier is anelectrical circuit that converts AC electrical power to a DC voltage andcascades its DC outputs to multiply the output voltage level, typicallyusing a network of capacitors and diodes/switches. In an exampleembodiment, the voltage multiplier is a Dickson multiplier.

FIG. 3 illustrates an example block diagram of a wireless IoT chip 300implementing a multiband energy harvester 200 according to anembodiment. In this embodiment, the wireless IoT chip 300 includes atransmit/receive antenna 310 that is not utilized for energy harvesting.

The harvester 200 is connected to a power management unit (PMU) 320coupled to the logic circuitry 330 of the wireless IoT chip 300. The PMU320 is an electronic circuit that performs general circuit power relatedoperations, such as supply regulation, voltage and current references,power on indication, brown-out indication, power modes control,management of power storage units, and more. The PMU 320 provides avoltage threshold crossing indication based on the measurement of thevoltage over an energy storage (e.g., a capacitor) 340.

In an embodiment, the PMU 320 provides multi-level voltage levelindications to the logic circuitry 330. These indications allow thelogic circuitry 330 to determine the state of a Voltage Supply at anygiven moment when the energy storage 340 charges or discharges.

In an embodiment, the PMU 320 includes a detection circuity (not shown)controlled by a controller (not shown). The detection circuity includesdifferent voltage reference threshold detectors, where, at any giventime, only a subset of such detectors are active to perform thedetection. The sub-set of detectors to be activated at any given momentis determined by the controller. A detailed description of the PMU 320designed to provide multi-level voltage indications is disclosed in U.S.patent application Ser. No. 16/176,460 assigned to the common assigneeand is hereby incorporated by reference.

The multiband energy harvester 200 includes a plurality of antennascoupled to a plurality of harvesting units as discussed in greaterdetailed above with reference to FIG. 2.

According to one embodiment, the multiband energy harvester 200 isconfigured to include two harvesting units connected to antennas thatcan harvest energy from signals received at the BLE advertisementchannels 2.426 GHz channel 38 and 2.48 GHz channel 39. Any subset of2.402, 2.426 and 2.428 may be used as well. Any combination of 1 to Xnumber of channels, signals and harvested inputs may be used. Forexample, all of the BLE advertisement channels may be used forharvesting energy. In addition, one or more Wi-Fi channels may bereceived in combination with the BLE channels. The primary as well asthe secondary BLE advertisement channels may be used for harvestingenergy.

According to one embodiment, the multiband energy harvester 200 isconfigured to include three harvesting units connected to antennas thatcan harvest energy signals received at the BLE frequency band 2.4 GHz,Wi-Fi band 2.4 GHz, and a Wi-Fi band 5GHz. In another embodiment, energyfrom signals transmitted by the BLE 5.0 may be harvested including oneor more advertisement channels. In yet another embodiment, BLE 5.0signals may be harvested as well as one or more cellular bands inaddition to one or more Wi-Fi bands. The BLE 5.0 is the latest versionof the BLE wireless communication.

In another embodiment multiband energy harvester 200 may be configuredto include a transmit/receive antenna, a 2.4 GHz antenna, a 1.8 GHz (PCScellular band) antenna and an ultra-short range 2.4 GHz harvestingantenna, which may be used for manufacturing high power consumption NVMburn.

It should be noted that the wireless IoT chip discussed herein mayinclude one or more sensors. Examples for such sensors include, but arenot limited to, temperature, humidity, weight, oxygen, CO2, pressure,location, bio-feedback, water, acoustic, light, and so on. In someconfigurations, the IoT chip may not include a sensor.

FIG. 4 illustrates an example diagram 400 of illustrating the antennasof a multi-band energy harvester designed according to one embodiment.Specifically, FIG. 4 illustrates 3 antennas 402, 404, and 406. In theexample arrangement, the antenna 402 is a 2.44 GHz centered transmitterantenna. The antenna 406 is a 2.402 GHz centered antenna. Similarly, theantenna 404 is a 5.2 GHz Wi-Fi antenna. Thus, in the arrangement shownin FIG. 4, the antennas 404 and 406 are utilized for energy harvestingwhile the antenna 402 is utilized for receiving and transmittingsignals.

FIG. 5 illustrates an example diagram 500 of a multi-band energyharvester designed according to another embodiment. As shown in FIG. 5,the design includes antennas 502, 504, 506, and 508. The antenna 502 isa sub-GHz loop antenna which encircles the rest of the structures forcompactness and other higher frequency loop antennas. In an embodiment,the antenna 502 operates at the cellular frequency band of 710 MHz andis utilized for energy harvesting. It should be noted that the antenna502 can be designed to operate in another cellular band or for RFIDfrequencies.

The antenna 506 also operates in the 1850 MHz cellular band and isutilized for energy harvesting. The antenna 504 is a 2450 MHz loopantenna serving as a receive/transmit antenna. The antenna 508 is a 2450MHz antenna loop antenna utilized for energy harvesting dedicated forhigh incoming RF power levels used during non-volatile memory (flash)programming. The antennas 504 and 508 operate in the ISM band. FIG. 5further illustrates electronic circuits of the IoT chip 510. It shouldbe noted that the energy for the programming of the non-volatile memorycan be harvested through other frequencies, not just in the 2450 MHzband.

The dimension of each harvesting and/or transmit/receive antennas (suchas the antennas discussed with reference to FIGS. 4-5) is determined insuch way that the center frequency of the antenna resonates with theelectronic circuits of the IoT chip. In an embodiment, each antenna isdesigned in such way that inductive elements of the antenna togetherwith capacitive elements of the chip would resonate. Specifically, in anembodiment, electrically small loop-antennas are used as the antennaelements. These antenna types inherit an inductive input impedance. Thecapacitive elements also include parasitic capacitance of the circuits.An electrically small loop antenna may comprise electrically small andlarge antennas. Typically, electrically small antennas having overallcircumference approaches of wavelength/5 or smaller, while electricallylarge loop antennas are those with a circumference of about free spacewavelength.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the principlesof the disclosed embodiment and the concepts contributed by the inventorto furthering the art, and are to be construed as being withoutlimitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosed embodiments, as well as specific examplesthereof, are intended to encompass both structural and functionalequivalents thereof. Additionally, it is intended that such equivalentsinclude both currently known equivalents as well as equivalentsdeveloped in the future, i.e., any elements developed that perform thesame function, regardless of structure.

As used herein, the phrase “at least one of” followed by a listing ofitems means that any of the listed items can be utilized individually,or any combination of two or more of the listed items can be utilized.For example, if a system is described as including “at least one of A,B, and C,” the system can include A alone; B alone; C alone; 2A; 2B; 2C;3A; A and B in combination; B and C in combination; A and C incombination; A, B, and C in combination; 2A and C in combination; A, 3B,and 2C in combination; and the like.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations are generally used herein as a convenient method ofdistinguishing between two or more elements or instances of an element.Thus, a reference to first and second elements does not mean that onlytwo elements may be employed there or that the first element mustprecede the second element in some manner. Also, unless statedotherwise, a set of elements comprises one or more elements.

1. A multi-band energy harvesting system, comprising: a plurality ofharvesting antennas, wherein each of the plurality of harvestingantennas operates at a specific frequency band; and a plurality ofharvesting units, wherein each of the plurality of harvesting units iscoupled to a respective harvesting antenna and adapted to harvest energyat the specific frequency band of the respective harvesting antenna. 2.The multi-band energy harvesting system of claim 1, further comprising:a power management circuit; and a capacitor for storing energy theharvested energy.
 3. The multi-band energy harvesting system of claim 1,wherein the power management circuit further comprises: a plurality ofdetectors, wherein each of the plurality of detectors are configuredwith a different reference threshold voltage level; and a controllercoupled to the plurality of detectors and configured to activate asubset of the plurality of detectors at any given time, wherein a subsetof the plurality of detectors, when activated, are configured to providea multi-level voltage level indication on a state of a voltage supply.4. The multi-band energy harvesting system of claim 1, wherein theharvested energy is utilized to power a wireless chip.
 5. The multi-bandenergy harvesting system of claim 1, wherein an antenna of the pluralityof harvesting antennas is a loop antenna.
 6. The multi-band energyharvesting system of claim 1, wherein an antenna of the plurality ofharvesting antennas is a centered antenna.
 7. The multi-band energyharvesting system of claim 1, wherein the specific frequency band ofeach of the plurality of antennas is any one of: a Bluetooth low energy(BLE) advertising channel frequency band, an Industrial, Scientific, andMedical (ISM) frequency band, a cellular commutation frequency band, aWi-Fi frequency band, and a Wi-Gig frequency band.
 8. The multi-bandenergy harvesting system of claim 1, wherein the plurality of harvestingantennas includes at least: a first harvesting antenna operates at theWi-Fi frequency band and a second harvesting antenna operates at the BLEfrequency band.
 9. The multi-band energy harvesting system of claim 1,wherein the plurality of harvesting antennas includes at least: a firstharvesting antenna operates at the Wi-Fi frequency band and a secondharvesting antenna operates at the BLE frequency band.
 10. Themulti-band energy harvesting system of claim 1, wherein the plurality ofharvesting antennas includes at least: a first harvesting antennaoperates at a first cellular communication frequency band, a secondharvesting antenna operates at a second cellular communication frequencyband, and a third harvesting antenna operates at the 2.4 GHz ISMfrequency band.
 11. The multi-band energy harvesting system of claim 1,wherein one of the harvesting antennas is configured to transmit andreceive communication signals.
 12. The multi-band energy harvestingsystem of claim 1, wherein each of the harvesting units includes avoltage multiplier coupled to the respective harvesting antenna andconfigured to harvest energy from over-the-air signals.
 13. Abattery-free wireless device, comprising: a multi-band energy harvestingsystem adapted to harvest energy from over-the-air signals transmittedin different frequency bands; and a sensor powered by the harvestedenergy.
 14. The battery-free wireless device of claim 13, wherein themulti-band energy harvesting system further comprises: a plurality ofharvesting antennas, wherein each of the plurality of harvestingantennas operates at a specific frequency band; a plurality ofharvesting units, wherein each of the plurality of harvesting units iscoupled to a respective harvesting antenna and adapted to harvest energyat the specific frequency band of the respective harvesting antenna; apower management circuit; and a capacitor for storing energy theharvested energy.
 15. The battery-free wireless device of claim 14,wherein an antenna of the plurality of harvesting antennas is any oneof: a loop antenna and a centered antenna.
 16. The battery-free wirelessdevice of claim 14, wherein the specific frequency band of each of theplurality of antennas is any one of: a Bluetooth low energy (BLE)advertising channel frequency band, an Industrial, Scientific, andMedical (ISM) frequency band, a cellular commutation frequency band, aWi-Fi frequency band, and a Wi-Gig frequency band.
 17. The battery-freewireless device of claim 14, wherein the plurality of harvestingantennas includes at least: a first harvesting antenna operates at theWi-Fi frequency band and a second harvesting antenna operates at the BLEfrequency band.
 18. The battery-free wireless device of claim 14,wherein each of the harvesting units includes a voltage multipliercoupled to the respective harvesting antenna and configured to harvestenergy from the over-the-air signals.
 19. The battery-free wirelessdevice of claim 14, wherein the plurality of harvesting antennas arefabricated a same substrate carrying the battery-free wireless device.20. The battery-free wireless device of claim 14, wherein the pluralityof harvesting antennas is utilized for programming a non-volatilememory.